Process for agglomerating a latex, agglomerated latex obtained and its application of the modification of thermoplastic matrices to make them impact-resistant

ABSTRACT

The agglomeration of a latex of a polymer chosen from elastomers and thermoplastic resins is performed by mixing the latex to be agglomerated with an agglomerating latex consisting of: 
     (A) a polymer chosen from elastomers and thermoplastic resins; and 
     (B) a nonionic surface-active agent consisting of a block polymer containing at least one polyoxyethylene block and at least one block of a polymer chosen from vinyl, diene and acrylic and methacrylic ester polymers, 
     the said agglomerating latex being produced by the synthesis of the polymer defined under (A) during which (B) has been employed as a surfactant. The polyoxyethylene-polystyrene-polyoxyethylene triblock polymer may be mentioned among the surface-active agents (B).

This is a division of application Ser. No. 07/595,674, filed Oct. 11, 1990, which was a continuation of application Ser. No. 07/163,752 filed Feb. 12, 1988.

The present invention relates to a process for agglomerating a latex based on a polymer chosen from elastomers and thermoplastic resins, the latex obtained by this process, and its application to the modification of rigid thermoplastic matrices to make them impact-resistant. By way of examples, there may be mentioned the application of a polybutadiene-based latex to the preparation of acrylonitrile-butadiene-styrene (ABS) resins, or the application of multilayer acrylic latices or of SBR latices in the reinforcement of matrices based on methyl methacrylate and styrene, or, yet again, the application of multilayer acrylic latices in the reinforcement of polystyrene matrices.

It is known that latices consist of emulsions of polymers in water to which various agents have been added, such as emulsifying agents, stabilizers and the like, and that in most cases they are produced directly by emulsion polymerization. The purpose of the agglomeration process is to increase the size of the polymer particles in these emulsions.

For example, if the reaction rate of the monomers is low then, in order to avoid a waste of energy and time, particularly in the case of manufacture on industrial scale, it is advantageous to employ high polymerization rates which lead to small particle sizes, below 200 nm, and then to perform an agglomeration of these particles of intermediate size, enabling them to attain the size finally required.

Thus, to produce an ABS resin with good impact strength characteristics, it is necessary to have available a polybutadiene-based latex in which the particle sizes lie between 300 and 700 nm. Now, with the usual method of emulsion polymerization of butadiene, the particle sizes increase at a rate of only 10 nm per hour, with the result that the polymerization is carried out so as to produce latices in which the polymer particles are small in size (of the order of 80-200 nm), in order to subsequently make use of an agglomeration technique.

The principle of all the known techniques for agglomerating latices is the transition from a stable state in which the latex contains fine polymer particles to another stable state in which the latex contains large polymer particles, under the effect of a physical, chemical or physicochemical agent, it being possible for the final stable state to be ensured, if desired, by a poststabilization of the latex.

The agglomeration methods proposed in the literature may be subdivided into two categories according to whether they do not employ a chemical agent or whether, on the contrary, they do employ one.

The first of these, among which the cooling method and the pressure gradient method may be mentioned, have the advantage of not contaminating the latices and, consequently, not interfering with subsequent processing of the latter (for example, grafting in the case where ABS is produced from a polybutadiene latex) and with the properties of the resulting products.

The second methods employ, as chemical agents, either solvents such as benzene, toluene, acetone and mixtures of the benzene-alcohol type, because of their destabilizing and swelling action, or else electrolytes, salts or acids, which act by partial destruction of the emulsifier protection, or, yet again, hydrophilic polymers: polyvinyl alcohol, polyvinyl methyl ether, polyoxyethylene, acrylic polyelectrolytes, polyurethanes, polyethylene glycol (Carbamax 20M), carboxymethyl cellulose and polyvinylacetal.

However, all these known methods present the following disadvantages:

a high energy consumption;

a more or less pronounced formation of coagulum;

a limited and rather small size of the agglomerated particles;

a high dependence of agglomeration with relation to temperature and time; and

the difficulty of controlling and the difficulty of reproducing the size distribution of the agglomerated particles.

To overcome these disadvantages, European Patent No. 29,613 has already proposed a process for the agglomeration of latices based on rubbery polymers, this process consisting of adding to the latex to be agglomerated another latex (called an agglomerating latex) containing:

(1) a polymer other than that present in the latex to be agglomerated and less lipophilic than the latter, chosen from (a) the homopolymers of C₁ -C₁₂ -alkyl acrylates and methacrylates; and (b) the copolymers of ethylenically unsaturated monomers capable of forming water-insoluble homopolymers, and

(2) a nonionic surface-active agent consisting of a product of addition of ethylene oxide to organic compounds containing reactive hydrogen atoms in their molecules.

However, this known process has a number of disadvantages and limitations.

Firstly, it may be emphasized that since, in this known process, the polymer in the latex to be agglomerated must be other than that of the agglomerating latex, and since the principal latex to be agglomerated is polybutadiene, it is not possible to employ a polybutadiene latex as an agglomerating latex.

Secondly, the synthesis of the latex which agglomerates by adsorption of the agglomerating surfactant on the initial latex involves the presence of the anionic surfactant in the latter, which reduces the size of the agglomerated latex and can lead to a preagglomeration, or even to incipient precipitation of the agglomerating latex.

Thirdly, a bimodal population is invariably obtained in this known process.

The present inventors have found, surprisingly, that when the abovementioned surface-active agent (2) in the agglomerating latex was replaced by a copolymer containing at least one polyoxyethylene block and at least one block of a vinyl, diene, acrylic and methacrylic ester polymer, this multiblock polymer being, furthermore, that in whose presence the preparation of the agglomerating latex is carried out, then it was possible to avoid the disadvantages of the known process, namely:

on the one hand, that the polymers in the latex to be agglomerated and in the agglomerating latex can be identical and that, generally, the group of the polymers to be agglomerated can be widened to the thermoplastic polymers without this making it necessary to perform the agglomeration at a temperature above the glass transition temperature of the polymer to be agglomerated, as is the case with the process described in European Patent No. 29,613, which is also limited to the use of rubbery polymers to be agglomerated;

on the other hand, that it is readily possible to produce agglomerated particles of large size; and

lastly, that a monomodal or bimodal population may be obtained at will, according to the value of the ratio of the mass of agglomerating polymer in 100 g of final latex to the mass of the polymer to be agglomerated in 100 g of final latex, and this forms a completely unexpected feature of the present invention.

In addition, the use of the abovementioned multiblock copolymer offers the additional advantages of making it possible to perform the agglomeration in a wide range of temperatures and in a wide range of solids contents of the agglomerating latex and of the latex to be agglomerated (it is possible, in particular, to work at much lower values of solids contents in the agglomerating latex than in the known process); and to attain a percentage of agglomerated particles of 100%.

The subject of the present invention is therefore a process for agglomerating a latex of a polymer chosen from elastomers and thermoplastic resins, characterized in that the latex to be agglomerated is mixed with an agglomerating latex consisting of:

(A) a polymer chosen from elastomers and thermoplastic resins; and

(B) a nonionic surface-active agent consisting of a block polymer containing at least one polyoxyethylene block and at least one block of a polymer chosen from vinyl, diene and acrylic and methacrylic ester polymers,

the said agglomerating latex being produced by the synthesis of the polymer defined under (A) during which (B) has been employed as surfactant.

Among the polymers of the latices to be agglomerated and the agglomerating latices, particular mention will be made of homopolymers and copolymers of butadiene, isoprene, styrene, alpha-methylstyrene, vinyltoluenes, acrylonitrile, and alkyl esters of acrylic, methacrylic, maleic, fumaric, crotonic and itaconic acids, in which the alkyl group contains from 1 to 12 carbon atoms, it being also possible for the latices to be agglomerated to be SBR latices or multilayer (bi- or trilayer) acrylic latices of a structure known as "core-shell".

A nonionic surface-active agent (B) consisting of a triblock polymer, preferably a polymer containing two terminal polyoxyethylene blocks, will preferably be chosen. A nonionic surface-active agent (B) consisting of a diblock polymer may equally be employed.

Furthermore, a polymer in which the block(s) other than the polyoxyethylene block(s) consists (or consist) of polystyrene will be chosen in particular. Thus, there may be mentioned the surfactant B which consists of the polyoxyethylene-polystyrene-polyoxyethylene triblock copolymer, referred to hereinafter as POE-PS-POE.

In addition, the surfactant (B) will advantageously have the following characteristics:

a number average molecular mass of between 1000 and 1,000,000; and

a polyoxyethylene content ranging from 5 to 95% by weight.

The surfactants (B) employed in the process according to the present invention are generally prepared by an anionic route, and this has the advantage of resulting in practically pure products. In the case of the preparation of the POE-PS-POE copolymer, the PS block is initiated by difunctional initiators of the "alpha-methylstyrene tetramers" type in tetrahydrofuran at a temperature of -80° C. The POE block is then polymerized at a temperature of 30° C.

In accordance with a preferred embodiment of the present invention, the latex to be agglomerated which is employed is prepared by emulsion polymerization in the presence of an anionic surface-active agent such as potassium laurate and sodium dodecylsulphate (SDS), a free-radical initiator such as potassium persulphate and a chain transfer agent such as tert-dodecyl mercaptan, and at a temperature of the order of 40° and 90° C. The polymer particle diameter in the latex to be agglomerated is, in particular, between 50 and 300 nm and the solids content of the said latex is between 5 and 50% by weight.

Similarly, use will be made, in particular, of an agglomerating latex in which the particle diameter of the polymer (A) will lie between 60 and 500 nm and which has a solids content of between 1 and 40% by weight.

In accordance with the invention, the agglomerating latices are prepared by emulsion polymerization in the presence of the nonionic surface-active agent (B), which enables them to be obtained directly. The polymerization also takes place in the presence of a free-radical initiator such as potassium persulphate. The presence of a chain transfer agent, such as tert-dodecyl mercaptan, is found to be practically essential; the purpose of this agent is to limit the chain length and it also acts as an initiator in the organic phase. An alcohol, such as methanol, may also be added to the mixture, and this acts as a cosurfactant and produces a marked decrease in the particle size by significantly reducing the interfacial tension between the particles and the solvent; this enables the latex particle size to be adjusted. Another surfactant, such as sodium laurylsulphate, could, furthermore, be employed for the same purpose. The polymerization is carried out batchwise or semicontinuously, at a temperature of the order of 40° to 90° C. (for example 70° C.). The conversion is very high and can reach 100%.

The diameter of the polymer particles in the agglomerating latices is a function of the monomers employed (thus, it appears to be lower for butyl acrylate than for butadiene and styrene), of the concentration of alcohol acting as a cosurfactant (as indicated above) and of the process employed (the semicontinuous process results in much smaller particle sizes than the batch process); furthermore, particle diameter diminishes with rising concentrations of copolymer (B, of cosurfactant alcohol and of initiator; on the other hand, an increase in the particle size is observed when the molecular mass Mn of the copolymer (B) increases.

In order to perform the agglomeration the procedure may be to add the agglomeration latex to the latex to be agglomerated, or to add the latex to be agglomerated to the agglomeration latex. It has been found, in fact, that the mixing method employed to produce the agglomeration has practically no effect on the diameter of the resulting agglomerated particles, except for special cases. In general, in practice it is preferable to follow the first method, because it is easy to add the agglomerating latex (a very small volume, in principle) to the latex to be agglomerated (a very large volume, in principle).

Furthermore, the agglomeration mixing according to the invention is performed for a period of time which, as a general rule, is between one minute and 48 hours; similarly, this mixing is carried out at a temperature which may lie between 10° C. and 100° C.

In accordance with the present invention, the agglomerating latex is introduced in a quantity of at least 0.05 part by weight of the solid polymer (A) and of at least 0.0001 part by weight of the surface-active agent (B) per 100 parts by weight of the polymer present in the latex to be agglomerated. In particular, the agglomerating latex may be introduced in a quantity corresponding to 0.05 -20 parts by weight of the solid polymer (A) and of 0.0001-0.2 part by weight of the surface-active agent (B) per 100 parts by weight of the polymer present in the latex to be agglomerated. It should be emphasized, nevertheless, that the quantities indicated above are not critical at all.

In accordance with a feature of the present invention which is of great interest, it has become apparent that, as a general rule, all the curves representing the size of the agglomerated particles as a function of the value of the ratio of the mass of agglomerating polymer to that of the polymer to be agglomerated in 100 grams of final latex exhibit a maximum, the population obtained being bimodal or monomodal, according to whether R is lower or higher than the value corresponding to this maximum. This represents a finding which is of great interest, when compared with the agglomerations produced in the process described in the abovementioned European Patent 29,613.

The morphology of the agglomerated particles is generally spherical and the surface of these particles is smooth. Moreover, the agglomerated particles obtained are stable thermally (freezing-thawing cycle), to ultrasound, to postaddition of agglomerating latex and to shear stresses.

It has thus been possible to produce agglomerated particles which have a size of up to 1700 nm.

The present invention also relates to the agglomerated latices produced by the process just defined and to the application of these agglomerated latices to the modification of thermoplastic matrices to make them impact-resistant. These matrices consist, in particular, of rigid thermoplastic polymers of at least one monomer chosen from alkyl methacrylates in which the alkyl group contains from 1 to 4 carbon atoms, styrene, substituted styrenes, acrylonitrile and methacrylonitrile, or of polymers with more than 50% by weight of at least one of the abovementioned monomers and at least one other ethylenically monounsaturated copolymerizable monomer. Examples of application have been mentioned in the introduction to this specification. The methods for preparing these reinforced matrices are traditional methods, which are known to the specialist. In general, the agglomerated particles are subjected to a coating process before flocculation, washing and drying, the final stage being dispersion in the matrix.

Various agglomerations of latices, which have been performed using the process according to the present invention will be described below in greater detail, by way of guidance and without implying any limitation. The latices employed in these examples have been designated by LPB, LS, LPBA and LSBR in the case of latices to be agglomerated of polybutadiene, polystyrene, poly(butyl acrylate) and of butadiene-styrene copolymer respectively, and by LPBCop, LPSCop, LPBACop and LPBA-SCop, in the case of the agglomerating latices of polybutadiene, polystyrene, poly(butyl acrylate) and butyl acrylate-styrene copolymer respectively, Cop denoting the triblock POE-PS-POE copolymer which is the nonionic surfactant in the presence of which the preparation of the agglomerating latex took place. The percentages indicated in the examples which follow are given by weight.

I--PREPARATION OF THE LATICES TO BE AGGLOMERATED 1) Preparation of Polybutadiene Latex

The following are introduced in succession into an 8-l reactor, after the stirring has been started up gradually to run at 500 revolutions/minute: 500 g of water, 6.3 g of lauric acid dissolved beforehand in 200 g of water, 1.75 g of potassium hydroxide, 2.10 g of tertdodecyl mercaptan (TDM), 1.40 g of potassium hydroxide dissolved in 50 g of water, and a rinse of 5000 g of water. The whole reactor is deoxygenated by being subjected to vacuum and then by the introduction of nitrogen at a pressure of 3 bars. It is heated to 70° C. 2.8 g of potassium persulphate, dissolved beforehand in 100 g of water, are added through an airlock and under nitrogen pressure, followed by a rinse with 50 g of water.

The polybutadiene latices LPB1to LPB6, whose characteristics are given in Table 2 below, were successfully prepared in this manner, while the pressure was varied.

2) Pressure of the Other Latices to be Agglomerated

a) General Operating Procedure

Water, the surfactant and sodium hydroxide are employed at a constant temperature of 70° C., with stirring and under a nitrogen stream. After the surfactant has completely dissolved, the mixture of monomer and TDM is added. After 10 min, when the temperature has become steady again, potassium persulphate, dissolved beforehand in water, is added.

b) Preparation of Polystyrene and Poly(butyl acrylate) Latices

The above general operating procedure was followed in order to prepare the individual latices as shown in Table 1 below, the characteristics of these latices also being given in Table 2 below.

                                      TABLE 1                                      __________________________________________________________________________     Latex          Surfactant                                                                               K.sub.2 S.sub.2 O.sub.8                                                              Potassium                                       to be  Monomer mass                                                                               Mass  mass  hydroxide mass                                                                         TDM mass                                agglomerated                                                                          introduced  introduced                                                                           introduced                                                                           introduced                                                                             introduced                              prepared                                                                              (g)     Type                                                                               (g)   (g)   (g)     (g)                                     __________________________________________________________________________     LPS    100     lauric                                                                             3.03  0.40  0.85    0.3                                                    acid                                                            LPBA 1 100     lauric                                                                             0.80  0.40  0.80    0.3                                                    acid                                                            LPBA 2 160     SDS 4.85  0.39  0       0.4                                     __________________________________________________________________________

3) Characteristics of the Latices to be Agglomerated Prepared According to 1) and 2)

                  TABLE 2                                                          ______________________________________                                         Type of                                                                        latex to                                                                               Mean     Standard  Solids                                              be agglom-                                                                             .0.      deviation content                                                                               Surface tension                              erated  (nm)     (nm)      (%)    (newton/cm)                                  ______________________________________                                         LPB1*   203      51.5      30.6   71.3 × 10.sup.-5                       LPB2**  181      48.4      30.7   60.1 × 10.sup.-5                       LPB3    112      33.2      31.0   72.6 × 10.sup.-5                       LPB4    104      27.8      32.2   73.2 × 10.sup.-5                       LPB5    100      24.1      32.3   72.1 × 10.sup.-5                       LPS      75      25        16.9                                                LPBA1   139      26        33.1                                                LPBA2   125      22        32.9                                                ______________________________________                                          *Highly crosslinked latex                                                      **Sparsely crosslinked latex                                             

II--PREPARATION OF AGGLOMERATING LATICES 1) POE-PS-POE Triblock Copolymeric Surfactants

The characteristics of these surfactants are shown in Table 3, which follows:

                  TABLE 3                                                          ______________________________________                                                 %      Mn of the   Mn of each                                                                             Mn of the                                   Cop     PS     PS block    POE block                                                                              Cop.                                        ______________________________________                                         1       40.5   2400        1800    6000                                        2       16.1   2400        6300    15000                                       3       21.0   1600        3000    7600                                        4       18.4   1600        3600    8800                                        5       21.0   1800        3400    8600                                        6       17.8   1800        4200    10200                                       7        9.1   1800        9000    19800                                       ______________________________________                                    

2) General Operating Procedure for Preparing these Agglomerating Latices by the Batch Process

Water, the Cop surfactant and methanol are introduced into a 1-l glass reactor thermostated with a water bath at a constant temperature of 70° C.; the residual air is removed by continuous bubbling of nitrogen. The reactor is stirred at a speed which will remain constant at 250 revolutions/min. After the Cop surfactant has completely dissolved and when the temperature has reached 70° C., the mixture of monomer(s) and TDM is added. After 10 min, when the temperature has become steady again, potassium persulphate dissolved in 15 g of water is added, the addition of the persulphate marking the beginning of the reaction.

3) General Operating Procedure for Preparing These Agglomerating Latices by the Semicontinuous Process

The procedure is initially as indicated in paragraph 2), except that 30% of the mixture of monomer and TDM is added and, 5 min later, all of the initiator, dissolved in water. The polymerization is then allowed to take place to 100% conversion, which results in the "seed" latex. The remaining 70% of the mixture of monomer and TDM is then added continuously at a rate of 0.3 ml/min.

4) Preparation of Various Agglomerating Latices

The above general operating procedures were followed to prepare the individual latices as shown in Table 4 below, in which the characteristics of these latices are also given.

                                      TABLE 4                                      __________________________________________________________________________     Type of                                                                               POE-PS-POE   Mono-                   Standard    Surface                agglomerat-                                                                           surfactant                                                                             K.sub.2 S.sub.2 O.sub.8                                                             mer(s)                                                                              Transfer agent                                                                         MeOH Mean dia-                                                                            deviation                                                                           Conversion                                                                            tension                ing latex                                                                             mass (g)                                                                               (g)  mass (g)                                                                            mass (g)                                                                               mass (g)                                                                            meter (nm)                                                                           (nm) (%)    (newton/cm)            __________________________________________________________________________     LPBACop1                                                                              4       0.1  65   0.4     60   197   43.1 99.8                          LPBACop2                                                                              4       0.1  65   0.4     60   155   37.8 90.0                          LPBACop3                                                                              4       0.1  65   0.0     60   117   31.2                               LPBACop4a                                                                             4       0.1  65   0.4     60   135   32.5 92.5   45.6 ×                                                                   10.sup.-5              LPBACop4b                                                                             4       0.1  65   0.4      0   197   64.4 69.0   46.9 ×                                                                   10.sup.-5              LPBACop4c                                                                             5       0.1  65   0.4     60   114   32.4 99.9   45.1 ×                                                                   10.sup.-5              LPBACop7                                                                              4       0.1  65   0.4     60   185   52.4 88.0   46.6 ×                                                                   10.sup.-5              LPSCop4                                                                               4       0.1  65   0.4     60   186   44.9 100.0  47.8 ×                                                                   10.sup.-5              LPBCop4                                                                               8       0.2  130  0.8     120  225   70.5 52.0   45.3 ×                                                                   10.sup.-5              LPBCop5                                                                               8       0.2  130  0.8     120  277   108.0                                                                               70.0   45.7 ×                                                                   10.sup.-5              LPBCop7                                                                               8       0.2  130  0.8     120  330   90.2 31.0   46.3 ×                                                                   10.sup.-5              LPBA-SCop6                                                                            4       0.5  50(BA)                                                                              0.0     60   138   37.9                                                   15(S)                                                      __________________________________________________________________________

III--AGGLOMERATION PROCESSES 1) General Operating Procedure

Various proportions of agglomerating latices of different concentrations were added by means of a burette, with mechanical stirring, to different types of latices to be agglomerated. Unless indicated otherwise, a uniform initial mass of 30 g of latex to be agglomerated was chosen. A gentle stirring by means of a bar magnet is provided during the addition of the agglomerating latex. This stirring is continued for a few minutes after the addition of agglomerating latex, and it is then stopped.

2) Concentration Units Chosen

In the following text, R denotes the ratio of the mass of agglomerating polymer in 100 g of final latex to the mass of polymer to be agglomerated in 100 g of final latex. If it is assumed that:

m₁ =mass of agglomerating polymer

m₁ ^(L) =mass of agglomerating latex

x₁ =solids content of the agglomerating latex and

m₂ =mass of polymer to be agglomerated

m₂ ^(L) =solids content of the latex to be agglomerated, then ##EQU1##

If C is the final solids content expressed in total mass of polymer in 100 g of latex, ##EQU2## [Cop] is the mass of POE-PS-POE triblock copolymeric surfactant added per 100 g of latex to be agglomerated expressed as solids content. The ratio I=D₉₀ /D₁₀ has also been defined, where D₉₀ and D₁₀ refer to the cumulative diameters forming 90% and 10% of the particle volume respectively.

3) Agglomeration of the Polybutadiene Latices by POE-PS-POE Triblock Copolymeric Acrylic Agglomerating Latices

a) Influence of the Mixing Method

Latex to be agglomerated: LPBA (φ=104 nm; x₂ =32.2%)

Agglomerating latex: LPBACop 4a (φ=135 nm; x₁ =4.52%)

                  TABLE 5                                                          ______________________________________                                                            Agglomerated latex                                                                                 Standard                                     R ×                                                                              C         (Cop) ×                                                                          Mean .0.                                                                               deviation                               Test 10.sup.+2                                                                              g/100 g   10.sup.+2                                                                              (nm)    (nm)                                    ______________________________________                                         1*   0.46    31.30     0.029   201     VB                                           0.92    30.47     0.058   450     172                                          1.17    30.07     0.072   607     VB                                           1.41    23.68     0.087   605     210                                          1.84    28.11     0.116   490     149                                          2.82    27.58     0.174   438     138                                          4.23    25.81     0.241   390     115                                     2**  0.87    30.57     0.053   402     142                                          0.97    30.40     0.059   450     151                                          1.09    30.19     0.067   542     181                                          1.25    29.92     0.076   612     163                                          1.46    29.58     0.089   573     157                                          1.75    29.12     0.107   510     141                                          2.19    28.45     0.134   449     116                                          2.92    27.42     0.179   392      96                                          4.38    25.60     0.268   386     110                                          8.77    21.54     0.537   302      76                                     ______________________________________                                          *Agglomeration temperature: 17° C.                                      **Agglomeration temperature: 25° C.                                     VB = very large                                                          

In test 1, the agglomerating latex was added to the latex to be agglomerated and, in test 2, the latex to be agglomerated was added to the agglomerating latex.

It is found that the mixing method employed to produce the agglomeration has no particular influence in this case on the diameter of the agglomerated particles.

b) Influence of Time on the Agglomeration Method

Latex to be agglomerated: LPB3 (x₂ =31.0%)

Agglomerating latex: LPBACop 3

                  TABLE 6                                                          ______________________________________                                                        Agglomerated latex                                                    Agglomerating                    Standard                                      latex added R ×                                                                             Time  Mean .0.                                                                               deviation                               Test  x.sub.1 (%) 10.sup.+2                                                                             (h)   (nm)    (nm)                                    ______________________________________                                         3*    2.4         0.78   0.06  195     73.0                                                             0.13  204     73.9                                                             0.25  209     78.7                                                             0.50  212     83.2                                                             1.5   215     81.5                                                             48.0  216     85.1                                    4**   4.8         3.13   0.02  264     89.3                                                             0.2   347     126                                                              0.4   382     99.8                                                             0.5   372     124                                                              0.8   400     122                                                              1.0   446     163                                                              1.25  461     168                                                              1.75  476     170                                                              2.0   476     167                                                              48.0  493     173                                     ______________________________________                                          *final solids content: C = 28.40                                               **final solids content: C = 28.61                                        

The time t=0, the beginning of the agglomeration, is taken from the end of the addition of the agglomerating latex to the polybutadiene latex.

Agglomeration of a latex of this type is fast, since, depending on the system under consideration, the final diameter is obtained after a few minutes to approximately one hour.

c) Influence of the Respective Concentrations of the Latex to be Agglomerated and of the Agglomerating Latex

1--Variation of the particle size as a function of the total concentration C at constant R

Latex to be agglomerated: LPB5

Agglomerating latex: LPBACop4a

Agglomeration temperature: 25° C.

                  TABLE 7                                                          ______________________________________                                                                                   Stan-                                                                          dard                                                                     Mean  devia-                                    X.sub.1                                                                               X.sub.2                                                                               R ×                                                                           C      Time .0.   tion  D.sub.90                       Test (%)    (%)    10.sup.+2                                                                           g/100 g                                                                               (h)  (nm)  (nm)  D.sub.10                       ______________________________________                                         5    4.5    32.3   1.39 29.77  0.01 282   99    2.2                                                           0.16 357   115   2.2                                                           0.33 368   126   2.3                                                           0.76 394   121   2.2                                                           1.91 445   137   2.1                                                           3.08 457   157   2.2                                                           22.0 545   187   2.0                            6    2.2    16.1   1.37 14.83  0.01 141   45    2.0                                                           0.25 173   57    2.1                                                           0.50 186   65    2.3                                                           1.00 195   67    2.0                                                           2.50 199   68    2.2                                                           24.0 280   98    --                             7    1.1     8.0   1.38  7.37  0.01 103   22    1.8                                                           1.00 106   22    1.8                                                           4.00 113   26    1.8                                                           24.0 143   42    --                             ______________________________________                                    

2--Variation in the size of the agglomerated particles as a function of R at constant C

Latex to be agglomerated: LPB3 (x₂ =31%)

Agglomerating latex: LPBACop 3

Agglomeration temperature: 17° C.

                  TABLE 8                                                          ______________________________________                                                                         Mean  Standard                                      X.sub.1                                                                               R ×                                                                             C      Time  .0.   deviation                                                                             D.sub.90                          Test (%)    10.sup.+2                                                                             g/100 g                                                                               (h)   (nm)  (nm)   D.sub.10                          ______________________________________                                         3    2.4    0.78   28.39  0.06  195    73    2.3                                                         0.13  204    74    2.2                                                         0.25  209    78    2.3                                                         0.50  212    83    2.3                                                         1.5   215    81    2.3                                                         48.0  216    85    2.1                               8    4.8    1.56   28.51  1     530   185    --                                                          24    580   233    --                                4    4.8    3.13   29.05  0.02  264    89    2.1                                                         0.2   347   126    2.1                                                         0.4   382    99    2.2                                                         0.5   372   124    1.7                                                         0.8   400   122    1.9                                                         1.0   446   163    2.1                                                         1.25  461   168    2.1                                                         1.75  476   170    1.8                                                         2.0   476   167    2.2                                                         48.0  493   173    1.9                               ______________________________________                                    

3--Variation in the size of the agglomerated particles as a function of time (R and C variable)

Latex to be agglomerated: LPB4 or LPB5

Agglomerating latex: LPBCop 4a (x₁ =4.5%)

Agglomeration temperature: 25° C.

                  TABLE 9                                                          ______________________________________                                                                         Mean  Standard                                      X.sub.2                                                                               R ×                                                                             C      Time  .0.   deviation                                                                             D.sub.90                          Test (%)    10.sup.+2                                                                             g/100 g                                                                               (h)   (nm)  (nm)   D.sub.10                          ______________________________________                                         5    32.3   1.39   29.77  0.01  282    99    2.2                                    (LPB5)               0.16  357   115    2.2                                                         0.33  368   126    2.3                                                         0.76  394   121    2.2                                                         1.91  445   137    2.1                                                         3.08  457   157    2.2                                                         22.0  545   187    2.0                               9    16.1   0.69   15.04  0.01  175   104    2.1                                    (LPB5)               0.16  189   127    2.0                                                         0.33  192   118    2.2                                                         1.91  250   129    2.2                                                         2.50  270   110    2.2                                                         24.0  354   127    2.1                               2    32.2   0.87   30.57  24.0  402   142    1.9                                    (LPB4) 0.97   30.40  24.0  450   151    2.0                                           1.09   30.19  24.0  542   181    2.0                                           1.25   29.92  24.0  612   163    2.0                                           1.46   29.58  24.0  573   157    1.9                                           1.75   29.12  24.0  510   141    1.8                                           2.19   28.45  24.0  449   116    1.8                                           2.92   27.42  24.0  392    96    1.8                                           4.38   25.60  24.0  386   110    1.9                                           8.77   21.54  24.0  302    76    2.0                               ______________________________________                                    

4--Discussion

It is found that the change in the size of the agglomerated particles shows a strong dependence on the agglomeration time, on R and on C. In all cases, when C is high, the agglomeration process is fast and virtually immediate.

d) Effect of Temperature

Latex to be agglomerated: LPB3 (x₂ =31.0%)

Agglomerating latex: LPBACop3(x₁ =4.82%)

R×10¹⁰⁺² =3.10

C (g/100 g)=26.63

                  TABLE 10                                                         ______________________________________                                                   Agglomerated latex                                                                                     Standard                                              T      Time       Mean .0.                                                                              deviation                                    Test     (°C.)                                                                          (h)        (nm)   (nm)                                         ______________________________________                                         10       65     0.02       286    103                                                          0.18       303    102                                                          0.20       299    109                                                          0.50       298    105                                                          1.00       304    114                                                          1.50       329    121                                                          2.00       315    113                                                    Heating stopped                                                               11     2.25       448    153                                                          2.75       458    153                                                          6.00       491    147                                          ______________________________________                                    

It is found that the increase in agglomeration temperature results in a fairly large decrease in the diameter of the agglomerated particles. In fact, the maximum diameter reached during the agglomeration at T=170° C. is 480 nm, whereas it is only 300 nm at T=65° C. On the other hand, if the heating is stopped at this diameter and the agglomeration temperature is set at T=11° C. as quickly as possible, a continued growth is observed in order to reach a final diameter of 490 nm, which is similar to the diameter obtained in an agglomeration at a low temperature (T=17° C.).

e) Effect of the Characteristics of the Agglomerating Latices

1--Influence of the molecular mass of the POE blocks on the agglomeration of the polybutadiene latex LPB4 (x₂ =32.2%; φ=104 nm).

Agglomeration temperature: 17°0 C.

Agglomeration time: 24 h.

                                      TABLE 11                                     __________________________________________________________________________                                  Agglomerated latex                                                                   Standard                                    Agglomerating latex                                                                            R ×                                                                         C    [Cop] ×                                                                       Mean .0.                                                                             deviation                                   Test                                                                              Type    X.sub.1 (%)                                                                         10.sup.+2                                                                         g/100 g                                                                             10.sup.+2                                                                           (nm)  (nm)                                        __________________________________________________________________________     11 LPBACop1                                                                               4.81 0.74                                                                              30.89                                                                               0.043                                                                               250   VB                                                          1.49                                                                              29.71                                                                               0.085                                                                               425   158                                                         2.48                                                                              28.28                                                                               0.143                                                                               556   187                                                         4.48                                                                              25.88                                                                               0.257                                                                               410   149                                         12 LPBACop4a                                                                              1.13 0.35                                                                              29.37                                                                               0.021                                                                               166    58                                                         0.70                                                                              27.02                                                                               0.042                                                                               219   VB                                                          1.05                                                                              25.04                                                                               0.084                                                                               303   113                                         13         2.26 0.70                                                                              29.47                                                                               0.043                                                                               244   VB                                                          2.10                                                                              25.29                                                                               0.087                                                                               474   189                                          1         4.52 0.46                                                                              31.30                                                                               0.029                                                                               201   VB                                                          0.92                                                                              30.47                                                                               0.058                                                                               450   172                                                         1.17                                                                              30.07                                                                               0.072                                                                               607   VB                                                          1.41                                                                              29.68                                                                               0.087                                                                               605   210                                         14              1.41                                                                              29.68                                                                               0.087                                                                               605   220                                                         1.41                                                                              29.68                                                                               0.087                                                                               597   VB                                           1              1.84                                                                              28.11                                                                               0.116                                                                               490   149                                         14              2.82                                                                              27.58                                                                               0.174                                                                               455   137                                          1              2.82                                                                              27.58                                                                               0.174                                                                               438   138                                                         4.23                                                                              25.81                                                                               0.241                                                                               390   115                                         14              4.23                                                                              25.81                                                                               0.241                                                                               404   117                                         15 LPBACop7                                                                               1.06 0.32                                                                              29.37                                                                               0.021                                                                               172   VB                                                          1.09                                                                              25.01                                                                               0.084                                                                               380   VB                                          16         4.24 0.43                                                                              31.29                                                                               0.029                                                                               191   VB                                                          0.86                                                                              30.45                                                                               0.058                                                                               363                                                               1.10                                                                              30.04                                                                               0.072                                                                               790                                                               1.32                                                                              28.67                                                                               0.087                                                                               1396                                                              2.64                                                                              27.54                                                                               0.174                                                                               766                                                               3.96                                                                              25.74                                                                               0.241                                                                               607                                               17 LPBACop2                                                                               1.10 0.34                                                                              29.37                                                                               0.021                                                                               170   VB                                          18         4.41 0.45                                                                              31.30                                                                               0.029                                                                               210                                                               0.67                                                                              30.46                                                                               0.042                                                                               263                                                               0.90                                                                              30.10                                                                               0.058                                                                               382                                                               1.13                                                                              30.06                                                                               0.072                                                                               635                                                               1.35                                                                              29.61                                                                               0.087                                                                               905                                               19              1.35                                                                              29.61                                                                               0.087                                                                               915                                               18              1.58                                                                              28.10                                                                               0.102                                                                               700                                                               2.71                                                                              27.56                                                                               0.174                                                                               638                                               19              4.06                                                                              25.81                                                                               0.241                                                                               481                                               __________________________________________________________________________      VB = very large                                                          

2--Influence of the molecular mass of the POE blocks on the polybutadiene latices LPB2 (x₂ =30.7%; φ=181 nm) and LPB1 (x₂ =30.6%; φ=203 nm)

Agglomeration temperature: 17° C.

Agglomeration time: 24 h.

                                      TABLE 12                                     __________________________________________________________________________     Polybuta-                           Agglomerated latex                            diene                                                                               Agglomerating latex                                                                           R ×                                                                         C    [Cop] ×                                                                       Mean .0.                                                                            Standard                              Test                                                                              latex                                                                               Type   X.sub.1 (%)                                                                        .0. (nm)                                                                           10.sup.+2                                                                         (g/100 g)                                                                           10.sup.+2                                                                           (nm) deviation                             __________________________________________________________________________     20 LPB2 LPBACop4a                                                                             1.13                                                                               135 0.37                                                                              28.01                                                                               0.022                                                                               450  161                                                          1.10                                                                              23.87                                                                               0.066                                                                               471  154                                   21             4.52    0.49                                                                              29.85                                                                               0.030                                                                               377  VB                                    22                     1.47                                                                              28.32                                                                               0.091                                                                               528  229                                   21                     1.47    0.091                                                                               492  VB                                    23                     2.94                                                                              26.33                                                                               0.182                                                                               373  146                                   22                     2.94    0.182                                                                               388  124                                   23                     4.41                                                                              24.65                                                                               0.273                                                                               320   95                                   22                     4.41         337   55                                   21                     4.4          391  151                                   24      LPBACop7                                                                              1.06                                                                               185 0.35                                                                              28.00                                                                               0.022                                                                               666  VB                                    25             4.24    1.38                                                                              28.29                                                                               0.091                                                                  4.14                                                                              24.59                                                                               0.273                                           26 LPBA LPBACop4a                                                                             4.52    1.47                                                                              28.22                                                                               0.022                                                                               610  VB                                                   4.52    2.95                                                                              26.25                                                                               0.182                                                                               450  153                                                  4.52    4.43                                                                              24.58                                                                               0.273                                                                               385  VB                                    __________________________________________________________________________

3--Influence of the initial concentration of POE-PS-POE triblock copolymeric surface active agent

Latex to be agglomerated: LPB4 (x₂ 32.2%: φ=104 nm)

Agglomeration temperature: 17° C.

Agglomeration time: 24 h.

                                      TABLE 13                                     __________________________________________________________________________                                  Agglomerated latex                                                                  Standard                                     Agglomerating latex  R ×                                                                         [Cop] ×                                                                       Mean .0.                                                                            deviation                                    Test                                                                              Type   X.sub.1 (%)                                                                        Mean .0. (nm)                                                                         10.sup.+2                                                                         10.sup.+2                                                                           (nm) (nm)                                         __________________________________________________________________________     12 LPBACop4a                                                                             1.13                                                                               135    0.35                                                                              0.021                                                                               166   58                                                               0.70                                                                              0.042                                                                               219  VB                                                                1.05                                                                              0.084                                                                               303  113                                           1        4.52       0.46                                                                              0.029                                                                               201  VB                                                                0.92                                                                              0.058                                                                               450  172                                                               1.17                                                                              0.072                                                                               607  VB                                                                1.41                                                                              0.087                                                                               605  210                                                               1.84                                                                              0.116                                                                               490  149                                                               2.82                                                                              0.174                                                                               455  137                                                               4.23                                                                              0.241                                                                               390  115                                          27 LPBACop4c                                                                             1.21                                                                               114    0.75                                                                              0.054                                                                               358  125                                          28        4.84       0.75                                                                              0.054                                                                               268  101                                          29                   1.00                                                                              0.072                                                                               461  VB                                                                1.25                                                                              0.109                                                                               574  VB                                           28                   1.25                                                                              0.109                                                                               544  193                                          30                   1.25                                                                              0.109                                                                               539  192                                          29                   1.75                                                                              0.145                                                                               475  164                                                               2.00                                                                              0.182                                                                               470  142                                                               2.50                                                                              0.218                                                                               405  104                                                               3.00                                                                              0.255                                                                               394  136                                          28                   3.00    415  130                                                               4.51                                                                              0.401                                                                               392  138                                          29                   4.51    365  104                                          28                   7.51                                                                              0.545                                                                               329  137                                          __________________________________________________________________________      VB = very large                                                          

It is found that more or less extensive agglomeration is obtained depending on the type and the concentration of the POE-PS-POE triblock surfactant employed. It appears that the higher the Mn of the POE blocks, the larger the diameter of the agglomerated particles.

4--Influence of the particle size of the agglomerating latex

Agglomerating latex: LPBACop4b (φ=197 nm)

Agglomeration temperature: 17° C.

Agglomeration time: 24 h.

                                      TABLE 14                                     __________________________________________________________________________                                  Agglomerated latex                                                             Mean Standard                                        Polybutadiene latex                                                                           X.sub.1                                                                           R ×                                                                         [Cop] ×                                                                       .0.  deviation                                    Test                                                                              Type                                                                               X.sub.2 (%)                                                                        Mean .0. (nm)                                                                         (%)                                                                               10.sup.+2                                                                         10.sup.+2                                                                           (nm) (nm)                                         __________________________________________________________________________     31 LPB4                                                                               32.2                                                                               104    1.06                                                                              0.32                                                                              0.021                                                                               167  VB                                                                0.64                                                                              0.041                                                                               247  VB                                                                1.09                                                                              0.084                                                                               359  VB                                           32                4.24                                                                              1.32                                                                              0.087                                                                               644  VB                                                                2.64                                                                              0.174                                                                               623  210                                                               3.96                                                                              0.241                                                                               658  171                                          33 LPB2                                                                               30.7                                                                               181    1.06                                                                              0.34                                                                              0.022                                                                               365  116                                                               1.05                                                                              0.066                                                                               461  VB                                           34                4.24                                                                              1.41                                                                              0.091                                                                               965  VB                                           35                   4.24                                                                              0.273                                                                               1634                                              __________________________________________________________________________      VB = very large                                                          

The sizes of the agglomerated particles obtained clearly depend on the size of the agglomerating latex particles. This effect, perceptible in the case of small-sized particles, becomes very considerable when the size of the particles to be agglomerated is large.

4--Agglomeration of the polybutadiene latex with agglomerating latices of POE-PS-POE triblock polybutadiene copolymers

a) Influence of the molecular mass of the POE blocks

Latex to be agglomerated: LPB5 (φ=100 nm; x₂ =32.3%)

Agglomerating latices: LPBCop5 (φ=225 nm; x₁ =2.5%)

Agglomerating latices: LPBCop6 (φ=277 nm; x₁ =3.6%)

Agglomeration temperature: 25° C.

                  TABLE 15                                                         ______________________________________                                                              Agglomerated latex                                             Agglo-            C                  Standard                                  merating  R       (g/100                                                                               [Cop] Mean φ                                                                            deviation                            Test latex     ×10.sup.+2                                                                       g)    ×10.sup.+2                                                                     (nm)   (nm)                                 ______________________________________                                         36   LPBCop5   0.67    29.92 0.074 132    47                                                                      (0.5)                                                                          135    49                                                                      (48)                                        37   LPBCop5   1.34    27.89 0.148 173    64                                                                      (0.5)                                                                          179    66                                                                      (48)                                        38   LPBCop5   2.58    24.85 0.285 214    81                                                                      (48)                                        39   LPBCop5   3.09    23.78 0.342 245    92                                                                      (48)                                        40   LPBCop5   7.73    17.40 0.856 324    95                                                                      (48)                                        41   LPBCop5   10.31   15.27 1.142 335    109                                                                     (48)                                        42   LPBCop6   1.1     29.69 0.085 216    79                                                                      (0.5)                                                                          227    83                                                                      (48)                                        43   LPBCop6   2.2     27.51 0.171 275                                                                            (48)                                        ______________________________________                                    

b) Influence of the particle size of polybutadiene

Latex to be agglomerated: LPB5 (φ=100 nm; x₂ =32.3%)

Latex to be agglomerated: LPB2 (φ=181 nm; x₂ =30.7%)

Agglomerating latex: LPBCop5(φ225 nm; x₁ =2.5%)

Agglomeration temperature: 25° C.

                  TABLE 16                                                         ______________________________________                                                              Agglomerated latex                                             Polybut-          C                  Standard                                  atiene    R       (g/100                                                                               [Cop] Mean φ                                                                            deviation                            Test latex     ×10.sup.+2                                                                       g)    ×10.sup.+2                                                                     (nm)   (nm)                                 ______________________________________                                         36   LPB5      0.67    29.92 0.074 135    49                                   37             1.34    27.89 0.148 179    66                                   38             2.58    24.85 0.285 214    81                                   39             3.09    23.78 0.342 245    92                                   40             7.73    17.40 0.856 324    95                                   44   LPB2      0.81    28.13 0.090 232    67                                   45             1.63    26.01 0.180 240    35                                   46             2.44    24.00 0.270 256    63                                   47             3.24    22.64 0.361 284    68                                   48             8.14    16.60 0.901 323    82                                   ______________________________________                                          *Mixing method employed = addition of polybutadiene latex to the               agglomerating latex.                                                     

According to the results obtained, it is found that the agglomeration employing the abovementioned latices is a function of the method of mixing the two latices (it is sometimes necessary to choose to add the latex to be agglomerated to the agglomerating latex), of the surfactant concentration, of the initial size of the polybutadiene latex and of the molecular mass of the POE blocks, and hence of the size of the agglomerating latex.

5--Agglomeration of polybutacrylate latices by POE-PS-POE triblock acrylic copolymer agglomerating latices

Latex to be agglomerated: LPBA1 (φ=139 nm; x₂ =23.1%)

Agglomerating latex: LPBACop4a (φ=135 nm; x₁ =4.45%)

Agglomeration temperature: 25° C.

                  TABLE 17                                                         ______________________________________                                                            Agglomerated latex                                                                                 Standard                                     R        C         [Cop]  Mean φ                                                                             deviation                               Test ×10.sup.+2                                                                        (g/100 g) ×10.sup.+2                                                                      (nm)    (nm)                                    ______________________________________                                         49*  1.5      29.75     0.098  153     42                                           3.5      26.31     0.230  177     34                                           7.3      22.97     0.496  218     31                                           8.9      21.79     0.586  238     70                                           13.6     18.85     0.898  260     --                                           22.6     15.22     1.496  260     64                                      ______________________________________                                          *LPBA1 prepared in the presence of potassium laurate as a surfactant.    

6--Other agglomerations

a) Agglomeration of polybutadiene latices by the POE-PS-POE triblock butylacrylic-styrenic copolymer agglomerating latices

Latex to be agglomerated: LPB4 (100 =104 nm; x₂ =32.2%)

Agglomerating latex: LPBA-SCop6 (φ=138 nm; x₁ =4.68%)

Agglomeration temperature: 25° C.

Agglomeration time: 24 h.

                  TABLE 18                                                         ______________________________________                                                            Agglomerated latex                                                                                 Standard                                     R        C         Cop    Mean φ                                                                             deviation                               Test ×10.sup.+2                                                                        (g/100 g) ×10.sup.+2                                                                      (nm)    (nm)                                    ______________________________________                                         50   1.48     31.31      0.028 191     VB                                           0.97     30.48      0.057 437     147                                          1.45     29.69      0.085 496     173                                          1.94     28.96      0.114 484     170                                          2.90     27.61      0.172 438     142                                          4.36     25.85      0.256 376     131                                     ______________________________________                                    

b) Agglomeration of poly(butyl acrylate) latices by the POE-PS-POE block butadiene copolymer agglomerating latices

Latex to be agglomerated: LPBA1 (φ=139 nm; x₂ =33.1%) or LPBA2 (φ=125 nm; x₂ =32.9%)

Agglomerating latex: LPBCop5 (φ=225 nm; x₁ =2.5%)

Agglomeration temperature: 25° C.

Agglomeration time: 48 hr.

                  TABLE 19                                                         ______________________________________                                                             Agglomerated latex                                                                                Standard                                     Latex to be                                                                               R       C       Mean φ                                                                            deviation                               Test Agglomerated                                                                              ×10.sup.+2                                                                       (g/100 g)                                                                              (nm)   (nm)                                    ______________________________________                                         51   LPBA1*     0.84    30.04   330    119                                     52   LPBA2**    0.75    30.13   329    VB                                      ______________________________________                                          *LPBA1: surfactant: potassium laurate                                          **LPBA2: surfactant: SDS                                                       VB = very large                                                          

c) Various agglomerations

                                      TABLE 20                                     __________________________________________________________________________                                Aggomerated latex                                                                   Standard                                          Latex to be                                                                           Agglomerating                                                                          R   C    Mean φ                                                                          deviation                                      Test                                                                              agglomerated                                                                          latex   ×10.sup.+2                                                                   (g/100 g)                                                                           (nm) (nm)                                           __________________________________________________________________________     53 LPS    LPBCop5 4.9 4.8  358  --                                             54 LPB*   LPSCop4 +                                                                              3.2 26.28                                                                               190  70                                                       SDS     6.5 24.85                                                                               223  82                                                               9.6 23.63                                                                               350  131                                            55 LPS**  LPBACop4a +                                                                            0.9 30.1 181  VB                                                       SDS     5.5 27.1 288  VB                                                               8.2 25.7 390  131                                                              13.7                                                                               23.4 280  89                                             __________________________________________________________________________      *LPB' (φ = 84.5 nm; x.sub.1 = 28.0%)                                       **LPS' (φ = 83.5 nm; x.sub.1 = 30.9%)                                      VB = very large                                                          

The present invention will be illustrated further by the following examples:

Two POE-PS-POE triblock polymers whose characteristics are shown in Table 21 below were used to prepare the agglomerating latices employed:

                  TABLE 21                                                         ______________________________________                                                             M of each POE                                              Cop    M of Cop*    block       % PS**                                         ______________________________________                                         8      77 000       15 000      20                                             9      25 000        4 000      33.3                                           ______________________________________                                          *determined by gel permeation chromatography;                                  **determined by the UV method based on the fact that ethylene oxide does       not absorb at a wavelength of 258 nm, only the PS block being detectable.

A series of LPBACop agglomerating latices were prepared according to the following general operating procedure:

"Into a 2-1 reactor are introduced: water, methanol if desired, in weight percentages shown in Table 22 below, 23% by weight of butyl acrylate together with, based on the monomer, 6% by weight of triblock polymer and 0.6% by weight ob TDM. The reactor is heated up to 70° C., at a stirring speed of 250 revolutions/min. When the temperature reaches 70° C., 0.15% by weight of K₂ S₂ O₈, based on the monomer, is added. The synthesis time is set at 4 hours."

The above operating procedure was followed in order to prepare these various LPBACop latices, as shown in Table 22 below, in which the characteristics of these latices are also given.

Also shown in this table are the characteristics of a polystyrene latex prepared batchwise in a 2-1 reactor, the ingredients (91% by weight of water+cop 8, 9% by weight of styrene and 1% by weight of TDM) being charged into the reactor and heated to 90° C. at a stirring speed of 200 revolutions/min, potassium persulphate then being added and the synthesis time being at least 3 hours.

                  TABLE 22                                                         ______________________________________                                         Type of                                                                        agglomerating                                                                             %        % of       Mean φ                                                                            x.sub.1                                  latex      of water methanol   (nm)   (%)                                      ______________________________________                                         LPBACop 8a 77       0          340    23                                       LPBACop 8b 67       10         200    22.5                                     LPBACop 8c                     320    23                                       LPBACop 9a 55       22         130    19                                       LPBACop 9b 67       10         220    23                                       LPSCop 8   91       25         160    25                                       ______________________________________                                    

The characteristics of the latices to be agglomerated employed in this series of examples are shown in Table 23 below.

                  TABLE 23                                                         ______________________________________                                         Type of latex to                                                                             Mean φ   X.sub.2                                             be agglomerated                                                                              (nm)         (%)    pH                                           ______________________________________                                         LPB6*         100          30     10                                           LPB7          110          30     12                                           LPB8          150          30     12                                           LPBA3**       60           31     4.5                                          LPBA4**       75           28     4.5                                          LSBR          230          40     11                                           ______________________________________                                          *latex containing 10.sup.-2 mole of SDS per 100 g of latex.                    **synthesized with SDS as a surfactant.                                  

In order to produce the agglomeration, the agglomerating latex is added batchwise to the latex to be agglomerated, to which the SDS surfactant has been added where appropriate, with mechanical stirring. The temperature, the agglomeration time and all of the parameters affecting the development of the size of the agglomerated particles (measured by turbidimetry) have been studied.

a) Influence of the agglomeration time

Latex to be agglomerated: LPB6

Agglomerating latex: LPBA Cop 9a

Operating conditions: temperature: 20° C.; R=2×10⁻²

                  TABLE 24                                                         ______________________________________                                                      Time   Agglomerated latex                                         Test         (h)    Mean φ (nm)                                            ______________________________________                                         56           0.5    280                                                                     2      470                                                                     6      840                                                                     12     1010                                                                    24     1010                                                       ______________________________________                                    

After 12 hours' agglomeration the particle size is stable.

b) Influence of the respective concentrations of the latex to be agglomerated and the agglomerating latex

1--Variation of the size of agglomerated particles as a function of the total concentration C at constant R

Latex to be agglomerated: LPB8

Agglomerating latex: LPBACop8a

Operating conditions: temperature: 20° C.; R=2×10⁻², pH=12.

                  TABLE 25                                                         ______________________________________                                                C            Time   Agglomerated latex                                  Test   g/100 g      (h)    Mean φ (nm)                                     ______________________________________                                         58     30           1      300                                                                     24     430                                                 59     50           1      660                                                                     24     1000                                                ______________________________________                                    

2--Variation in the size of agglomerated particles as a function of R at constant C.

Latex to be agglomerated: LPB8

Agglomerating latex: LPBACop8a

Operating conditions:

temperature: 20° C;

time: 24 hours; pH=12

                  TABLE 26                                                         ______________________________________                                                            C        Agglomerated latex                                 Test   R × 10.sup.-2                                                                        g/100 g  Mean φ (nm)                                    ______________________________________                                         58     1           30       430                                                60     2           "        660                                                61     3           "        700                                                62     5           "        580                                                63     8           "        580                                                64     0.5         50       820                                                59     1           "        >1000                                              65     2           "        660                                                66     3           "        580                                                ______________________________________                                    

c) Influence of the characteristics of the agglomerating latices.

1--Influence of the particle size

Latex to be agglomerated: LPB8

Operating conditions:

temperature: 20° C.;

time: 24 hours; pH=8

                  TABLE 27                                                         ______________________________________                                                 Agglomerating           Mean φ                                     Test    latex          R × 10.sup.2                                                                      (nm)                                           ______________________________________                                         67      LPBACop8b      1        600                                            68      "              2        620                                            69      "              3        600                                            70      "              5        550                                            71*     "              7        480                                            72*     LPBACop8a      1        640                                            73*     "              2        >1000                                          74*     "              3        960                                            75*     "              5        780                                            ______________________________________                                    

2--Influence of the molecular mass of the POE blocks in the POE-PS-POE triblock polymers

Latex to be agglomerated: LPB8+1.5 10₋₄ mole of SDS/100 g of latex

Operating conditions:

temperature: 20° C.;

time 24 hours

                  TABLE 28                                                         ______________________________________                                                 Agglomerating           Mean φ                                     Test    latex          R × 10.sup.2                                                                      (nm)                                           ______________________________________                                         76      LPBACop9b      1        450                                            77      "              2        450                                            78      "              3        500                                            72      LPBACop8a      1        640                                            73      "              2        >1000                                          74      "              3        960                                            75      LPBACop9b      5        780                                            79      "              5        700                                            80      "              7        480                                            ______________________________________                                    

d) Influence of the characteristics of the latices to be agglomerated

1--Influence of the pH of the polybutadiene latices

Latex to be agglomerated: LPB8

Agglomerating latex: LPBACop8a

Operating conditions:

temperature: 20° C.

time: 24 hours

                  TABLE 29                                                         ______________________________________                                                              C      SDS    Agglomerated latex                          Test pH     R × 10.sup.2                                                                      g/100 g                                                                               mole 10.sup.4                                                                         Mean φ (nm)                             ______________________________________                                         64   12     0.5      50     0      820                                         59          1        "      "      >1000                                       65          2        "      "      660                                         66          3        "      "      580                                         63          8        "      "      580                                         81    8*    1        "      1.5    600                                         82          2        "      "      620                                         83          3        "      "      700                                         84          5        "      "      1000                                        85          7        "      "      820                                         58   12     1        30     "      430                                         60          2        "      "      660                                         61          3        "      "      700                                         62          5        "      "      580                                         63          8        "      "      640                                         72    8*    1        "      "      640                                         73          2        "      "      >1000                                       74          3        "      "      960                                         75          5        "      "      780                                         ______________________________________                                          *pH of the latex to be agglomerated adjusted to 8 by the addition of a         dilute solution of hydrochloric acid.                                    

2--Influence of the degree of covering of the latex to be agglomerated

Agglomerating latex: LPBCop8a

Operating conditions:

temperature: 20°0 C.;

time: 24 hours

                  TABLE 30                                                         ______________________________________                                                         Degree of                                                           Latex to be                                                                               covering         Agglomerated latex                            Test agglomerated                                                                              %         R × 10.sup.2                                                                    Mean φ (nm)                               ______________________________________                                         57   LPB7       >100      2      420                                           58   LPB8       80-85     1      430                                           60   "                    2      660                                           61   "                    3      700                                           62   "                    5      580                                           63   "                    8      580                                           ______________________________________                                    

The agglomeration is more pronounced in the case of the latex which has a lower degree of covering.

e) Other agglomerations

Operating conditions:

temperature: 20° C.

time: 24 hours

                  TABLE 31                                                         ______________________________________                                                                             Agglomerated                                     Agglomerating                                                                              Latex to be       latex                                      Test  latex       agglomerated                                                                              R × 10.sup.2                                                                    Mean φ (nm)                            ______________________________________                                         86    LPSCop 8    LPB8       1      430                                        87    "           "          2      450                                        88    "           "          3      700                                        89    "           "          5      550                                        90    "           "          7      460                                        91    LPBACop8c   LPBA3      1      185                                        92    "           "          3      200                                        93    "           "          5      420                                        94    "           "          7      550                                        95    "           "          10     840                                        96    "           "          15     800                                        97    "           "          20     545                                         98*  LPSCop8     LPBA4      1      230                                         99*  "           "          3      550                                        100   LPBACop8c   LSBR       ≧0.5                                                                           >1 μm                                   ______________________________________                                          *Addition of 10.sup.-4 mole of SDS per 100 g of latex to the latex to be       agglomerated.                                                             

We claim:
 1. An agglomerated latex produced by a process comprising mixing the latex to be agglomerated with an agglomerating latex,wherein said latex to be agglomerated is a polymer selected from the group consisting of elastomers and thermoplastic resins, wherein said agglomerating latex consists of:(a) a polymer (A) selected from the group consisting of elastomers and thermoplastic resins; and (b) a nonionic surface-active agent (B) which is a block polymer comprising at least one polyoxyethylene block and at least one block of a polymer selected from the group consisting of vinyl, diene and acrylic and methacrylic ester polymers, and wherein said agglomerating latex is produced by employing said nonionic surface-active agent (B) during the synthesis of polymer (A).
 2. An agglomerated latex according to claim 1, wherein the polymer of said latex to be agglomerated and said polymer (A), which are the same or different, are selected from the group consisting of homopolymers and copolymers of butadiene, isoprene, styrene, alphamethylstyrene, vinyltoluenes, acrylonitrile and alkyl esters of acrylic, methacrylic, maleic, fumaric, crotonic and itaconic acids in which the alkyl group contains from 1 to 12 carbon atoms.
 3. An agglomerated latex according to claim 1, wherein said latex to be agglomerated is a SBR latice or a multilayer acrylic latice.
 4. An agglomerated latex according to claim 1, wherein said nonionic surface-active agent is a triblock polymer.
 5. An agglomerated latex according to claim 4, wherein said nonionic surface-active agent is a triblock polymer containing two terminal polyoxyethylene blocks.
 6. An agglomerated latex according to claim 1 wherein said nonionic surface-active agent is a block polymer consisting of at least one polyoxyethylene block and at least one polystyrene block.
 7. An agglomerated latex according to any one of claims 1 to 6, wherein said nonionic surface-active agent has a number average molecular mass of between 1000 and 1,000,000.
 8. An agglomerated latex according to any one of claims 1 to 6, wherein said nonionic surface-active agent is from 5% to 95% by weight polyoxyethylene.
 9. An agglomerated latex according to claim 1, wherein said latex to be agglomerated is prepared by emulsion polymerization in the presence of an anionic surface-active agent.
 10. An agglomerated latex according to claim 9, wherein the polymer particles making up said latex to be agglomerated are between 50 and 300 nm in diameter and the solids content of said latex to be agglomerated is between 5% and 50% by weight.
 11. An agglomerated latex according to claim 1, wherein the polymer particles of (A) making up said agglomerating latex are between 60 and 500 nm in diameter and the solids content of polymer (A) is between 1% and 40% by weight.
 12. An agglomerated latex according to claim 1, wherein said mixing is carried out for a period of time between one minute and 48 hours.
 13. An agglomerated latex according to claim 1, wherein said mixing is carried out at a temperature of between 10°0 C. and 100° C.
 14. A method of improving the impact resistance of a thermoplastic matrix, comprising dispersing in said thermoplastic matrix an agglomerated latex as claimed in claim
 1. 15. A method of improving the impact resistance of a thermoplastic matrix as claimed in claim 14, wherein said thermoplastic matrix comprises (1) at least one polymer of at least one monomer chosen from alkyl methacrylates in which the alkyl group contains from 1 to 4 carbon atoms, styrene, substituted styrenes, acrylonitrile and methacrylonitrile, or (2) at least one polymer having more than 50% by weight of at least one of the monomers of (1) and at least one other ethylenically monounsaturated copolymerizable monomer.
 16. A rigid thermoplastic matrix having dispersed therein an agglomerated latex according to claim
 1. 17. A rigid thermoplastic matrix according to claim 16, wherein said thermoplastic matrix comprises (1) at least one polymer of at least one monomer chosen from alkyl methacrylates in which the alkyl group contains from 1 to 4 carbon atoms, styrene, substituted styrenes, acrylonitrile and methacrylonitrile, or (2) at least one polymer having more than 50% by weight of at least one of the monomers of (1) and at least one other ethylenically monounsaturated copolymerizable monomer. 